HEADQUARTERS THIRD DIVISION, THIRD CORPS,
Fair Oaks, June 18, 1862.

General BARNARD,

Chief Engineer and Aide-de-Camp, Army of the Potomac:

GENERAL: If you could possibly find leisure I wish that you would ride over to examine my position. It is a line echeloned on the left rear of Hooker's position. Our left is weak, as it depends solety on the swamp, which, if it dries, can be passed; still, I am strong. The meaning of my echelon is this, that I am near enough to cover with artillery (and by advancing, by rifle firing) the ground that the enemy would have to pass over in attacking Hooker's flank. My pieces are at the same time safe, and in doing this I have also an echelon protection for myself from Hooker. But Lieutenant McAlester, to whom General Heintzelman gives a carte blanche, is about constructing a redoubt midway between Hooker's redoubt and a battery that I have on my left. This thus converts my position from an echelon to an oblique potence, deprives me of an echelon defence from Hooker, and invetes attack on me as a principal face; against the desirableness of which two things oppose, viz, that this new redoubt is placed too near woods. If these woods are sufficiently cut down in front, it will oblige us in so doing to project even beyond Hooker's line of pickets, brings the work too near certain dangerous roads and debouches (open grounds) which the enemy possess in the rear, and exposes us to the same things that Heintzelman has already been punished for in the case of Casey's redoubt, surprised and captured by an unseen line of the enemy established in the woods too near him. The left as held by me is strong as a secondary position. The moment that it is converted into a primary one it is fearfully weak. Please, therefore, to visit these parts, and call on me or on General Berry, the senior brigadier in first line, for an explanation of the roads and debouches by which an enemy can advance. The second point, perhaps, is this-we possibly may be called on to act by this flank, and I should say that the enemy's attention is not to be taken from the Williamsburg road.

With best regards, yours, truly,

P. KEARNY,

Brigadier-General, Commanding Division, Third Corps.

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SPECIAL ORDERS,
HDQRS. FIFTH PROV. ARMY CORPS, Numbers 40. Camp near New Bridge, Va., June 18, 1862.

Brigadier-General McCall will early to-morrow morning camp two brigades in suitable position for defence and shelter against the fire of the enemy from opposite of Chickahominy of the east bank of the mill, near Mechanicsville and near Mechanicsville road. The Third Brigade will remain in camp in its present location prepared to support the first two or resist the crossing the Chickahominy by the enemy. From the first command will be sent to bivoac at Mechanicsville two regiments and a battery, which regiments will picket the line now picketed by the command at Mechanicsville. The Sixth [Eighth] Illinois Cavalry, now picketing toward Atlee's Station, and connecting with General Cooke's pickets, will under the command of the brigadier-general commanding the first two brigades, and Colonel Farnsworth will report to him. General McCall will assign batteries to the command.

By command of Brigadier General F. J. Porter:

FRED. T. LOCKE,
Assistant Adjutant-General.

[11.]